1. Field of the Invention
The present invention relates to a home-based cellular radio/cordless phone system, and in particular to a method of transmitting a caller""s identification number received by a home base station to a mobile instrument set to a cellular mode.
2. Description of the Related Art
Generally, a home-based cellular radio/cordless phone system includes a home base station and mobile instrument. The mobile instrument can be switched between a cordless phone mode and a cellular phone mode depending upon the mobile instrument""s location with respect to a home base station service area in order to communicate with the home base station. Accordingly, this type of phone system allows one to use the same mobile instrument as a cellular phone for cellular network communications and as a cordless phone for low cost communications via the public switched telephone network (PSTN).
The home base station typically includes the ability to receive a caller""s identification number (ID Number) from the PSTN and transmit it to the mobile instrument while in the cordless phone mode. However, this feature may only be performed when the mobile instrument is within the home base station service area. Hence, in order for the mobile instrument to receive the caller""s ID Number received by and transmitted from the home base station, the mobile instrument should be within the home base station service area.
For example, as shown in FIG. 1, in a prior art telephone system, when the mobile instrument or station 110 is within the home base station service area 130 and set to the cordless phone mode, the caller""s ID number can be transmitted from public exchange system 100 through PSTN to the home base station 110 and then to the mobile station 120. However, when the mobile station is set to the cellular phone mode, it cannot receive the caller""s ID Number.
Accordingly, it is an object of the present invention to provide a method of transmitting a caller""s ID number received by a home base station to a mobile station set to the cellular phone mode.
According to the present invention, a method of transmitting a caller""s ID Number received by a home base station located within a predefined home base station area to a mobile instrument or station set to a cellular phone mode is provided. The method comprises the steps of receiving the caller""s ID Number along with a ring signal at the home base station, determining whether the mobile instrument is set to the cellular phone mode, transmitting the caller""s ID Number to the mobile instrument if the mobile instrument is set to the cellular phone mode, storing the caller""s ID Number in the home base station if the mobile instrument is not set to the cellular phone mode while continuously checking to detect whether the mobile instrument is set to the cellular phone mode and transmitting the caller""s ID Number to the mobile instrument after detecting the mobile instrument has been set to the cellular phone mode, setting a flag at the home base station to represent receipt of the caller""s ID Number by the mobile instrument, performing communication via the mobile instrument after clearing the flag when the mobile instrument is detected to have changed to a communication mode by receiving the ring signal, determining whether the flag has been set in the home base station if the ring signal is terminated without performing communication, transmitting the caller""s ID Number to the mobile instrument set to the cellular phone mode upon detecting the flag, and clearing the flag upon completing the transmission of the caller""s ID Number.